Rats (and Mice)!

Some good news with the South Georgia Heritage Trust declaring that this Antarctic island is finally rodent free (https://www.theguardian.com/environment/2018/may/09/south-georgia-declared-rat-free-centuries-rodent-devastation). The rats and mice were inadvertently introduced to the island by whaling (and explorers?) ships that anchored there in Victorian times. These rodents decimated ground- and burrow-nesting birds (more than 80 species)  that bred on this previously predator-free zone. The rodents could take eggs and chicks and presumably survived the winter in constructed burrow systems. The rodents were only removed by repeatedly dropping tons of poisoned bait from helicopters in many locations in the 350k hectare island. Conveniently, the island is separated by glaciers into a number of locations that act almost like islands (the rats and mice cannot cross the ice to re-populate cleared areas). There was a concern that some birds (notably the South Georgia pintail) would take the poison bait but these populations can rapidly recover by movement from adjoining locations. The absence of rodents (it is difficult to confirm absolutely) was aided by 3 trained dogs who failed to sniff any out after many kilometres of searching. South Georgia is also an important seal-breeding location so it was important not to poison these animals but these animals operate on the coastal fringe.